DESCRIPTION (Applicant's Abstract): Repeated exposure to an item within a task shows clear effects on performance. After a single repetition, response times are decreased and response selection is biased -- a phenomenon referred to as priming. After many repetitions, response times become even faster, responses become stereotyped, and tasks requiring considerable attention resources in their naive state are performed effortlessly in their practiced state. While these patterns have been well characterized at the behavioral level, the functional-anatomic changes that take place to allow task facilitation are only beginning to be explored. Pilot data show that recently developed functional magnetic resonance imaging (fMRI) methods are able to observe activation changes in human brain regions as cognitive tasks are facilitated by repetition. The goal of the present research proposal is to use fMRI to track changes that allow cognitive task facilitation in normal subjects. Brain areas activated by word and picture categorization tasks will be characterized in their naive state and will be tracked during early and late phases of item-repetition. After a single item-repetition, task facilitation is predicted to be accompanied by FMRI activation reductions in certain brain areas reflecting the increased efficiency of processing. These early effects may parallel behavioral findings related to priming and show anatomic specificity in relation to the specific task processes being facilitated (as proposed by the components of processing framework). As the number of repetitions increases, brain areas allowing flexible processing(e.g., prefrontal areas) are predicted to become less involved. Other areas, in this highly practiced state, will begin to take over performance of the tasks and are predicted to demonstrate gradually developing fMRI activation increases. This more slowly evolving effect may obey properties similar to skill acquisition and represent a transition to qualitatively distinct processing pathways being used in the over learned task state. The significance of doing this research is that data will be generated in a much needed area of basic research: the exploration of functional-anatomic changes that allow cognitive task performance to be come facilitated. Such information can provide a backdrop for comparing compromised or compensatory functional anatomy that might be observed in patient populations. Recovery following brain damage, for example, occurs gradually and rehabilitation often relies on continuous practice with tasks. It thus seems likely that the principles by which normal brains are able to facilitate task performance and acquire new skills will extend to how the damaged brain acquires skills that were lost.